20929561 has 4 divisors (see below), whose sum is σ = 21651300. Its totient is φ = 20207824.

The previous prime is 20929553. The next prime is 20929577. The reversal of 20929561 is 16592902.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 4648336 + 16281225 = 2156^2 + 4035^2 .

It is a cyclic number.

It is not a de Polignac number, because 20929561 - 2³ = 20929553 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20929501) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 360826 + ... + 360883.

It is an arithmetic number, because the mean of its divisors is an integer number (5412825).

Almost surely, 2^20929561 is an apocalyptic number.

It is an amenable number.

20929561 is a deficient number, since it is larger than the sum of its proper divisors (721739).

20929561 is an equidigital number, since it uses as much as digits as its factorization.

20929561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 721738.

The product of its (nonzero) digits is 9720, while the sum is 34.

The square root of 20929561 is about 4574.8837143691. The cubic root of 20929561 is about 275.5836024813.

The spelling of 20929561 in words is "twenty million, nine hundred twenty-nine thousand, five hundred sixty-one".